For the life of me I could not figure out why primal airs were going for 50-100 gold on the auction house. I knew that they were used in leveling some professions as well as twink enchants, so I understood why some level 80's might buy them. Then it hit me, no characters were ever encountering the air elementals while leveling! The two spots you can get primal air are shadowmoon valley and the elemental plateau: both of which a deathknight or other leveling character would never enter because the elemental plateau requires flying and shadowmoon valley is too high level; by then they would be in northrend leveling.

Thus you have a somewhat in demand item with literally no supply. Here's my video on where to farm primal airs, I would suggest parking an alt at either of these locations and then just logging in every once in a while to collect some airs.

i would say the demand for these [customers who have the gold you're after if you're reading sites like these] is for the encanting only. i doubt people are buying airs for xmutes. and i doubt any of the LW or BS recipes are selling [except for 70 twinks?????? do they exist?].

the boot/cloak/glove agility enchants are probably BiS for many PVP classes at the 29 level [i assume]. i assume at 29, maybe even 39, you can't get the northrend agility enchants.

and/or - i'd have to check the leveling of outland professions. perhaps the airs are for people finally gettig around to leveling their DK's professions, or their next "main-alt" after their main is now coming into ulduar gear.

maybe there's a point in the BS or enchanting path, for example, where these airs are the shortest leveling route.

I'd say you're right on the money for some of the enchants, especially cat's swiftness, cause that can make leveling a great deal faster, and with the leg armors. But beyond that it seems like an audience limited to engineers making their transports and completionists who need to make one of everything.